1. Understand the Reaction:

* Chlorine gas (Cl₂) reacts with fluorine gas (F₂) to form a gaseous product.

* The volume ratio of reactants is 1:3 (1 liter Cl₂ : 3 liters F₂).

* The volume ratio suggests a simple whole-number ratio of molecules in the balanced chemical equation.

2. Determine the Product's Empirical Formula:

* Since the volume ratio is 1:3, we can assume a single chlorine molecule reacts with three fluorine molecules.

* This means the empirical formula of the product is ClF₃ (one chlorine atom and three fluorine atoms).

3. Consider the Product's State:

* The problem states the product is a gas. This supports the idea of a simple covalent molecule like ClF₃, as ionic compounds are usually solids at room temperature.

Conclusion:

The most likely formula for the gaseous product is ClF₃ (chlorine trifluoride).